N62 minimum valve lift

[bcredliner]

Originally Posted by killcrap

I wouldnt call it logical since the AIR does not change the air fuel mixture strategy during the CAT warm up phase. How can the difference in ambient air temperature cause misfires? The secondary air system will come on a cold engine at 0° or 5°.

The problem here is not the AIR system, and is most likely cause by uneven cylinder filling.

OK

[Dellpc]

Thank you all for thinking along. Here are no wrong or right answers, it's just sharing you experience and knowledge. I think I can rule out the idea that valvetronic module is doing some weird stuff because as Cmyachtie tests showed, the valve lift was very low while starting in cold and no problems with his car. This is the information I was looking for.

I can live with it probably. Today the car standed 10 hours in -12C and to keep him going to misfire I needed to hold the revs around 1200 rpm for a minute or two. Then it was ok to drive away.

I could add one option to the list of what you can do with this problem. I would need "MAF switch" installed to my car. Like a button that switches MAF off while starting the cold engine. When I unplugged the MAF the other day it ran fine, but mixture was rich judged by the smell. Therefore I can't run the car without MAF, but starting is definetely better without it.

[bcredliner]

Eliminating MAF cold start input is not a fix. You could have a failing MAF but usually there are symptoms at normal operating temp and associated error codes. While the attached is about an E46 much of it applies. Cold weather misfires and CEL, common issues $50 fix! - E46Fanatics

[cmyachtie]

Originally Posted by bcredliner

OK

I think I tend to agree about the uneven filling, however can you explain what if anything we can do about that?
I have just about eliminated any potential causes I have read about on the coldstart problem and as it is totally random for me and has been for the last 4 years, plugs are good, injectors are good, mac is good, no vacuum leaks etc.
Will attempt to post my list of faults occurred over the past year....look forward to any feedback, thanks

[bcredliner]

"OK" did not mean I agree with Killcrap. I disagree with his input about SAP. He asked a question and then declared it is not the SAP. That meant to me anything further would have initiated a urinary altercation. For instance, the SAP activates on cold starts and is active for about a minute until CAT is hot enough for the engine to go from open loop to closed loop. It doesn't have to get down to 0-5 degrees. It is activated in the middle of a Texas summer. Not saying the SAP is the problem just his explanation of why it isn't the SAP.

[Fast Eddie]

Run 87 octane fuel and see if that helps your misfire in a cold start situation. Helped/fixed a few cars at my shop that had similar issues. There was one that had 2-3 sets of intermediate levers installed, no fix but once it had 87 fuel put it never had the misfires again.

[cmyachtie]

Originally Posted by Fast Eddie

Run 87 octane fuel and see if that helps your misfire in a cold start situation. Helped/fixed a few cars at my shop that had similar issues. There was one that had 2-3 sets of intermediate levers installed, no fix but once it had 87 fuel put it never had the misfires again.

That is even more confusing for me as I have noticed having a lesser problem when I have a bottle of red line injector cleaner in my tank with 91 and I believe that would be just the opposite octane wise ???

Will,give it a go next fill up though and see what happens, after reading the above E46 link I was convinced it was going to be my fuel filter as I had come to think I experienced more during lower gastank levels until,I actually compiled the log for the year and noticed having just as many faults when tank was full....if I wasn't so damn stubborn I would just accept it as a N62 "feature"....and
Live with it....LOL

[Fast Eddie]

Originally Posted by cmyachtie

That is even more confusing for me as I have noticed having a lesser problem when I have a bottle of red line injector cleaner in my tank with 91 and I believe that would be just the opposite octane wise ???

Will,give it a go next fill up though and see what happens, after reading the above E46 link I was convinced it was going to be my fuel filter as I had come to think I experienced more during lower gastank levels until,I actually compiled the log for the year and noticed having just as many faults when tank was full....if I wasn't so damn stubborn I would just accept it as a N62 "feature"....and
Live with it....LOL

Yea I hear you it sounds ridiculous to do but we had similar issues on this motor at my BMW shop and had our 'puma' help us out and to our surprise it fixed the problem. When I get a 4.8is (hopefully in the next month) I'm gonna be running 87 all winter long. Good luck I hope it helps /fixes your issue. Keep me posted.

[cmyachtie]

Originally Posted by Fast Eddie

Yea I hear you it sounds ridiculous to do but we had similar issues on this motor at my BMW shop and had our 'puma' help us out and to our surprise it fixed the problem. When I get a 4.8is (hopefully in the next month) I'm gonna be running 87 all winter long. Good luck I hope it helps /fixes your issue. Keep me posted.

Will do, am @half tank now will be next week sometime.

[bcredliner]

Originally Posted by cmyachtie

Will do, am @half tank now will be next week sometime.

A 4.8 is designed to run on premium fuel. Unless 87 is premium in your area using lower octane in an engine designed for premium increases the risk of detonation (spark knock) which can cause major damage to an engine.

Please add your X5 year, model and engine in your signature. Much easier to help if that info is available.